It would seem that one of my personal banes has become inaccuracy in depictions of HAZMAT PPE. In this case, Level A HAZMAT protective gear is, well, only good for short durations. The air bottles usually used with Level A HAZMAT have 4500 cubic feet of air, IIRC, and they only last about 15 minutes, 20 minutes tops. Definitely not ideal for this sort of work. Level C HAZMAT (gas masks and NBC gear, basically) is much better suited for dealing with this sort of exploration, even if it provides less protection in theory.